Baseboard Management Controller (BMC)
Latest generation of servers (e.g. rp3410/rp3440) and workstations (e.g. C8000) have a BMC (baseboard management controller) that is active when the system is powered. When attached to the serial console, you can press ESC ( and you will be able to interact with the BMC:
ESC ( cli>help CLI Commands: C [<passwordstring>] - Change Password CON - Display Console selection FPL - Read Forward Progress Log H - Help (this text) I <ipmi command data> - Send any IPMI message req fmt: rsSA netfnlun chk1 rqSWID rqSeq cmd [data] chk2 resp fmt: rqSWID netfnlun chk3 rsSa rqSeqrsLun cmd ccode [data] chk4 INFO - Display BMC FW Revision IPMI <ipmi command data> - Send any IPMI message req fmt: netfnlun cmd [data] resp fmt: ccode [data] P [0,1] - Power Control Q - Quit/Logout RS [s] - Reset System [and switch to sys console] SD - Read SDR Repository SE - Read System Event Log TOC [s] - Send an INIT/TOC [and switch to sys console] cli>
This most useful for being able to remotely reboot (RS command) and power on/off (P command) the system. Pressing ESC ) "reconnects" one to the system's serial console.
The C8000 supports IPMI, and presumably a lot of these same things can be done over the built-in e1000 LAN interface once configured.
Thanks to Matt Turner <email@example.com> for above info.
In File:Lpv00338 rx2600 zx6000.pdf you can find a chapter with a broader description of the BMC.
Please note that most older parisc machines don't have a BMC, but instead a GSP, see GuardianServiceProcessor.